1. Field of the Invention
The present invention relates to an organic light emitting display device including a plurality of white sub-pixels.
2. Discussion of the Related Art
With the advancement of multimedia, the importance of flat panel display (FPD) devices is increasing. Therefore, various FPD devices such as liquid crystal display (LCD) devices, plasma display panel (PDP) devices, and organic light emitting display devices are being practically used. In such FPD devices, organic light emitting display devices have a fast response time, and have no limitation in a viewing angle because the organic light emitting display devices self-emit light. Accordingly, the organic light emitting display devices are attracting much attention as next generation FPD devices.
In general organic light emitting display devices, one unit pixel is configured with a red (R), green (G), and blue (B) sub-pixels, and an image of various colors is displayed through three sub-pixels.
Recently, a four-color organic light emitting display device in which a white (W) sub-pixel is added to a unit pixel is being developed to increase a luminance of the unit pixel. The four-color organic light emitting display device converts three-color input data of red, green, and blue into four-color data of red, green, blue, and white to display an image.
In driving a white color, a related art four-color organic light emitting display device continuously emits light from a white sub-pixel, and selectively emits light from two of red, green, and blue sub-pixels, thereby realizing a desired white color. That is, the related art organic light emitting display device generates, as white output data, the minimum grayscale value among input data of red, green, and blue, and subtracts the white output data from three-color input data of red, green, and blue to generate three-color output data of red, green, and blue. For example, in FIG. 1, when three-color input data Ri, Gi and Bi are composed of 20 (Ri), 30 (Gi), and 35 (Bi), the related art four-color organic light emitting display device converts the three-color input data Ri, Gi and Bi into four-color output data Ro, Go, Bo and Wo composed of 0 (Ro), 10 (Go), 15 (Bo), and 20 (Wo).
The above-described four-color organic light emitting display device was proposed on the assumption that color coordinates of a white sub-pixel are uniform. However, since a white organic light emitting element included in the white sub-pixel continuously emits light unlike other sub-pixels, the white organic light emitting element can be deteriorated relatively earlier than the other sub-pixels according to a material characteristic and an emission time, and a deterioration of the white organic light emitting element causes a reduction in white luminance and a change in color coordinates.
For this reason, in the related art four-color organic light emitting display device, color coordinates (CIEx, CIEy) are shifted depending on the deterioration of the white organic light emitting element to cause a yellowish image, and the change in color coordinates is shown like image sticking.